A platform used in agriculture harvesting crops is universally defined as a head attached to a harvesting machine and that serves as a removable attachment for use when cutting requirements are request. It is made and assembled onto a main frame or main frame which is divided into a central section, the area corresponding to coupling with the harvester, and two side sections—wings—, that projects on either side of said central section according to a perpendicular direction to the advance direction of the harvesting machine. The platform has a cutting mechanism—cutterbar—projecting laterally across the width thereof, defined in front of the side sections and center section, and is configured to sever the standing crop.
Platforms contain a system for the transverse movement of the crop material. Typically it is formed by a helical screw conveyor and alternately today there exist systems containing a set of canvas or drapers for conveying. Both the canvas—draper—and the screw conveyor operate to transport the crop cut by the cutterbar and drive it into the center section. Furthermore, it is well known there are multitudes of arrangements where gadgets are used to force the material that reaches the center section of platform to pass through the feederhouse—and to the combine's feeder thereof—, to be later threshed by the harvester. Each prior art heads prefer one of these devices and determine the input mode of the crop material to the feeder of the harvester.
It is known that the cutterbar of some cutting platform is configured to flex in response to ground shape. In these, a series of sliding plates—skid shoes—are linked to said cutterbar to confer the ability to settle above the ground and slipping while operating. All this in view of making the cut of the plant as close to the ground as possible in practice, allowing the collection of those pods with beans sprouting in the lower part of the stem. Thus, when the head is advanced in work, the cutterbar is positioned virtually glued to the ground and curling up to mimic the natural unevenness of the field, resulting into a crop cut at constant height. While this is well known in theory, most platform transitions from the flexible cutterbar to the auger/draper does not respect a good design of the cutterbar. In the chase of shortening the distance between the front edge of the draper conveyor and the cutting zone, most manufacturers have not developed a really effective, good angled, low losses cutterbar systems.
Traditional platforms—be it platforms using configurations according to prior art technologies—implemented for cutting crops such as soybeans, wheat, barley, safflower or bean (among others) usually comprise a single conveyor belt which projects forward from the main frame—in an oblique downward direction, describing a driving surface for the crop material that extends to the cutterbar, without interruption—. These arrangements have a number of drawbacks and limitations that separate the operation of the drapers from the ideal operation form. Firstly, the prior art usually platforms are constructed so that the angle formed by the upper run of the belt with the ground is too aggressive (large), so that there is greater potential for the loose grains to slide to the ground (and therefore lost from being processed).
Another drawback associated with these primitive configurations is that the beams which support the cutting mechanism are typically projected at an angle describing a great slope. As for some types of crops it is necessary that the cutterbar is as close to the ground as possible, it is common that the front ends of said beams are supported above the ground to slide over while the platform is advanced and therewith follow the natural contour. Reasonably, it often happens that the beams undergo a partial digging and consequently drag a part of the uppermost layer of the soil, and potentially breaking some mechanism of the platform.
Secondly, there is the design robustness necessary in the construction of each support arm. In prior art mechanisms, cantilevered loads appearing around the pivot axis of the beams tend to be enormous. This corresponds to the great length from the cutterbar to the fulcrum of the support beams. Support beams where designed to project from the rear of the platform—at the main frame—to the very front to hold the cutterbar, with the rotary point positioned on the rear of the beam and in this manner causing a huge lever effect.
Additionally, in prior art platforms there are some complications regarding the transmission mechanism used to power the cutterbar. In configurations that include a right angle drive (id est an L-type gearbox) for deriving power to the gearbox that mobilizes cutting sickle—and converts a circular motion to a linear alternating one—, it is used a shaft with universal joints at the ends as mean of ligation between the two gearboxes. Depending on the particular design, the input shaft of the sickle drive is positioned at a specific angle, and in order to cancel the non-uniformity of the rotational speed the output shaft of the L-type gearbox is placed in parallel to the first. However, when the cutterbar is requested to flex the sickle gearbox goes up and down therewith, and the angles of the universal joints vary. As a consequence, the needed torque for cutting the crop is much smaller than the claimed by the L-type gearbox. This indicates a severe power losses due to changing angles of the universal joints. Some manufacturers have included telescopic shafts to keep in the L-type gearbox input shaft parallel to the sickle drive input shaft, but it has resulted into premature failure of the Cardan transmission or into excessive robustness, expensive drive mechanisms for the cutterbar.
On the other side there are the constraints associated with traditional arrangements used to move the crop coming from the side sections to the open end of the main frame. Some well known use a transverse conveyor belt, which may be fixed to or floating relative to the cutterbar. This transverse draper covers the entire central section of the platform and determines a flat rigid surface that can vary its inclination relative to advance direction of the platform or the tilt with respect to the lateral draper conveyors, or both simultaneously. However, unlike the behavior related to the side draper conveyors, when the central portion of the cutterbar flexes to adapt to the natural curvature of field, the distance between the upper run of the transverse draper and said portion of the (bent) cutterbar is not constant. The latter happens because the cutterbar takes the form of a curve with multiple inflection points while the cross canvas defines a flat plane, so that the distance between the two geometries is not constant. This ended up into a dead zone defined between the front margin of the transverse conveyor and the corresponding portion of the cutterbar, that some manufacturers have intentionally called a rock trap, and is a region where the crop material flow is slowed down and where shelling occurs. Then, the approach to make the central portion of the cutterbar as flexible as possible tighten to the restriction of minimizing the dead zone resulted into a draper platform with central portion that is not so good at cutting crop height and no so good handling short, low volume crops.